staging: r8188eu: remove disable_interrupt from struct hal_ops

Remove disable_interrupt function pointer from struct hal_ops, as it
is unused.

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210906010106.898-7-phil@philpotter.co.uk


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>